TWI702590B - Electroluminescence display and method of managing defective pixels thereon - Google Patents

Abstract

An electroluminescence display and a method of managing defective pixels thereon are provided. Defective pixels are detected from the pixels, based on sensing results on the electrical characteristics of a driving element, and defect candidates are selected from among the pixels within a compensation range in which the electrical characteristics of the driving element can be compensated by a compensation value obtained based on the sensing results on the electrical characteristics of the driving element.

Description

Electroluminescence display and method for controlling defective pixels

The invention relates to an electroluminescent display capable of updating defective pixel information in real time and a method for controlling the defective pixels.

According to the material of the light-emitting layer, electroluminescent displays can be classified into inorganic light-emitting displays and organic light-emitting displays. Among them, the active matrix organic light emitting display includes an organic light emitting diode (hereinafter referred to as "OLED"), which is a typical self-luminous light emitting diode with fast response time, high luminous efficiency, high brightness, and wide viewing angle The advantages.

The pixels on the organic light emitting display all include an OLED and a driving element, and the driving element drives the OLED through the current supplied to the OLED according to the gate-source voltage. The OLED of an organic light emitting display includes an anode, a cathode, and an organic compound layer between these electrodes. The organic compound layer is composed of a hole injection layer (HIL), a hole transport layer (HTL), a light emitting layer (EML), an electron transport layer (ETL), and an electron injection layer (EIL). When a source voltage is applied to the anode and the cathode, the holes passing through the hole transport layer HTL and the electrons passing through the electron transport layer ETL move to the light emitting layer EML and form excitons. As a result, the light emitting layer EML generates visible light.

The driving element can be realized as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) TFT. For each pixel, the electrical characteristics of the driving element should be the same, but due to various reasons such as process changes and device characteristics changes, there may be changes between pixels, and may change with the passage of the driving time of the display. In order to compensate for the change in the electrical characteristics of the driving element, internal compensation and external compensation can be applied to the electroluminescent display. In the internal compensation method, the threshold voltage of the driving element is sampled, and the data voltage is compensated through the threshold voltage of the driving element. In the external compensation method, the change in the electrical characteristics of the driving element between pixels is compensated by sensing the voltage of each pixel, which changes with the electrical characteristics of the driving element, and is modulated by an external circuit based on the sensed voltage Enter the image data.

As the display driving time elapses, the bias stress of the gate is accumulated on the driving element and degrades the driving element. Due to the bias stress of the gate on the driving element, the threshold voltage of the driving element is shifted.

Before the electroluminescent display is shipped, the defective pixels on the screen are visually inspected through a testing process, and if the number of defective pixels on the product exceeds a preset allowable level, the product is considered defective. However, with the deterioration process of the driving element after the product is shipped, more defective pixels may appear, and there is no measure for controlling pixels with progressive defects.

Therefore, the present invention provides an electroluminescent display that can detect dark defects and control defective pixel information immediately after the product is shipped, and a method for managing defective pixels on it.

An exemplary aspect of the present invention provides an electroluminescent display, including: a display panel including a plurality of data lines, a plurality of gate lines crossing the data lines, and a plurality of pixels, each pixel Both include a driving element for driving a light-emitting diode; a compensating element configured to detect from the pixels based on the sensing results of the electrical characteristics of the driving element in each sub-pixel of the pixels Defective pixels, the sensing result is obtained by a sensing element connected to the driving element; and a memory is configured to store defective pixel information on the defective pixels.

Another exemplary aspect of the present invention provides an electroluminescent display, including: a compensation element, which sets a compensation value based on the sensing result of the electrical characteristics of the driving element in each sub-pixel of the plurality of pixels, the sensing The measurement result is obtained by a sensor connected to the driving element, and defect candidates are selected among pixels within a compensation range, wherein the electrical characteristics of the driving element are compensated by the compensation value; and a memory storing a Defect candidate information. The defect candidate information includes the number of defect candidates.

Another exemplary aspect of the present invention provides a method for controlling defective pixels on an electroluminescent display, the method comprising: detecting the defective pixels from the pixels based on a sensing result of the electrical characteristics of the driving element; The sensing result on the electrical characteristics sets a compensation value, and a defect candidate is selected from pixels within a compensation range, wherein the electrical characteristics of the driving element are compensated by the compensation value; and the information about the defective pixel and the defect candidate A defective pixel information is stored in a memory.

100‧‧‧Display Panel

101‧‧‧sub pixel

102‧‧‧Data line

103‧‧‧Sensing line (external compensation circuit)

104‧‧‧Gate line

1041‧‧‧First Gate Line

1042‧‧‧Second Gate Line

110‧‧‧Data Driver (Display Panel Drive Circuit)

110a‧‧‧Power Driver IC

111‧‧‧Sensing device (external compensation circuit)

112‧‧‧Demultiplexer (display panel drive circuit)

114‧‧‧Source printed circuit board

120‧‧‧Gate Driver (Display Panel Drive Circuit)

130‧‧‧Timing Controller

131‧‧‧Compensation part (external compensation circuit)

132‧‧‧Memory

132a‧‧‧volatile memory

132b‧‧‧Non-volatile memory

134‧‧‧Control Panel

140‧‧‧Power section

200‧‧‧Host System

210‧‧‧Wired/Wireless Network

300‧‧‧Service Center

AA‧‧‧Active area

AT‧‧‧effective interval

BP‧‧‧Vertical sync pulse start timing

Coled‧‧‧parasitic capacitance

Cst‧‧‧Capacitor

DAC‧‧‧Digital to Analog Converter

DATA‧‧‧Digital image data

DE‧‧‧Data enable signal (timing signal)

DT‧‧‧Drive components

FP‧‧‧Vertical sync pulse end timing

GMA‧‧‧Gamma reference voltage

Hsync‧‧‧Horizontal sync signal (timing signal)

M1‧‧‧First switching element (switching element)

M2‧‧‧Second switching element (switching element)

M3‧‧‧Switch element

M4‧‧‧Switch element

n1‧‧‧First node

n2‧‧‧second node

OFF‧‧‧Power-off sequence

OLED‧‧‧Organic Light Emitting Diode

ON‧‧‧Power-on sequence

SCAN‧‧‧Scan signal

SENSE‧‧‧Sensing signal

VB‧‧‧Vertical blanking interval

Vdata‧‧‧Data voltage

VDD‧‧‧Pixel drive voltage

VGH‧‧‧High gate voltage

VGL‧‧‧Low gate voltage

Vin‧‧‧Input voltage

Vref‧‧‧Reference voltage

VS‧‧‧Vertical blanking interval

VSS‧‧‧Low level power supply voltage

Vsync‧‧‧Vertical sync signal (timing signal)

Vth‧‧‧Critical voltage

μ‧‧‧Migration rate

S01~S04‧‧‧Step

S11~S17‧‧‧Step

S21~S35‧‧‧Step

The drawings included to provide a further understanding of the present invention and incorporated into and constitute a part of the present application illustrate the aspects of the present invention, and together with the description are used to explain the principle of the present invention. In the drawings: FIG. 1 is a block diagram showing an electroluminescent display according to an exemplary aspect of the present invention; FIG. 2 is a circuit diagram showing an external compensation circuit connected to a pixel circuit; FIG. 3 is a circuit diagram showing a connection to a display panel The view of the circuit board; Figure 4 is a view showing the volatile memory and non-volatile memory connected to the timing controller; Figure 5 is a view showing the inspection mode after the product is shipped; Figure 6 is a detailed display of the effective interval and A view of the vertical blanking interval; FIG. 7 is a flowchart showing a method for controlling defective pixels before the product is shipped in an electroluminescent display according to an exemplary aspect of the present invention; In an exemplary aspect of an electroluminescent display, a flow chart of a method for controlling defective pixels after the product is shipped; FIG. 9 shows in detail if the variation of the threshold voltage of the driving element is within the normal and compensable range in FIG. 8 , A flowchart of a method for controlling defective pixels; and FIG. 10 is a view showing an example of a user seeing a defect report on the screen and requesting after-sales service.

By referring to the following detailed description and drawings of exemplary aspects, it is possible to more easily understand the various aspects and features of the present invention and the methods for implementing them. However, the present invention can be implemented in many different forms and should not be construed as being limited to the exemplary aspects set forth herein. On the contrary, these exemplary aspects are provided to make the present invention thorough and complete, and to fully convey the concept of the present invention to those with ordinary knowledge in the field, and the present invention is defined by the scope of the attached patent application.

The shapes, sizes, ratios, angles, numbers, etc. shown in the drawings for describing the exemplary aspects of the present invention are merely examples and are not limited to those descriptions shown in the drawings. Throughout the specification, the same component symbols represent the same components. When describing the present invention, detailed descriptions of related conventional technologies will be omitted to avoid unnecessarily obscuring the present invention.

When using terms such as "including", "having", and "consisting of", as long as the term "only" is not used, other parts can be added. Unless explicitly stated otherwise, the singular form can be interpreted as the plural form.

Even if not explicitly stated, the components can be interpreted as including the error range.

When using terms such as "upper", "overlay", "below", "side" to describe the positional relationship between two parts, as long as the term "immediate" or "direct" is not used, one or more parts can be located here Between the two parts.

It should be understood that although terms such as first and second may be used to distinguish one element from another element, the function or structure of these elements should not be limited by these terms.

The features of the various exemplary aspects of the present invention may be partially or fully coupled or combined with each other, and may technically interact or work together in various ways. The exemplary aspects can be implemented individually or in relation to each other.

In the electroluminescent display of the present invention, the pixel circuit may include one or more of n-channel transistors (NMOS) and p-channel transistors (PMOS). The transistor may be implemented as an oxide transistor with an oxide semiconductor pattern or as an LTPS transistor with a low-temperature polysilicon semiconductor (LTPS) pattern. The transistor is a three-electrode device with gate, source and drain. The transistor can be implemented as a thin-film transistor (TFT) on the display panel. The source is the electrode that provides carriers for the transistor. The carriers in the transistor flow out from the power source. The drain is the electrode where the carriers leave the TFT. That is, the carriers in the transistor flow from the source to the drain. In the case of n-channel transistors (NMOS), the carriers are electrons, so the source voltage is lower than the drain voltage, so that electrons flow from the source to the drain. In an n-channel transistor (NMOS), current flows from the drain to the source. In the case of P-channel transistors (PMOS), the carriers are holes, so the source voltage is higher than the drain voltage, so that the holes flow from the source to the drain. In P-channel transistors (PMOS), since holes flow from source to drain, current flows from source to drain. It should be noted that the source and drain of the transistor are not fixed in place because the source and drain can be interchanged according to the applied voltage. In the following description, the source and drain of the transistor will be referred to as first and second electrodes.

The gate signal of the TFT used as a switching element swings between the gate-on voltage and the gate-off voltage. The gate-on voltage is set higher than the threshold voltage of the TFT, and the gate-off voltage is set lower than the threshold voltage of the TFT. The TFT is turned on in response to the gate-on voltage, and turned off in response to the gate-off voltage. In NMOS, the gate-on voltage can be the gate high voltage VGH, and the gate-off voltage can be the gate low voltage VGL. In PMOS, the gate-on voltage can be the gate low voltage VGL, and the gate-off voltage can be the gate high voltage VGH.

Hereinafter, various exemplary aspects of the present invention will be described in detail with reference to the accompanying drawings. In the following exemplary aspect, an electroluminescent display will be described, which is about an organic light emitting display including an organic light emitting material, but is not limited thereto.

The electroluminescent display according to the present invention operates in a normal driving mode for displaying an input image on the screen, and operates in a sensing mode for sensing electrical characteristics of pixels. In the normal driving mode, during the display driving period, the display panel driving circuit writes pixel data into the pixels in the effective part of each frame. In the sensing mode, the electrical characteristics of the driving element are sensed through the compensation value based on the sensing result and the pixel data of the input image is adjusted to compensate for the change in the electrical characteristics of the driving element in each sub-pixel.

FIG. 1 is a block diagram showing an electroluminescent display according to an exemplary aspect of the present invention. Fig. 2 is a circuit diagram showing an external compensation circuit connected to a pixel circuit.

1 and 2, the electroluminescent display according to an exemplary aspect includes a display panel 100 and a display panel driving circuit.

The screen of the display panel 100 includes an active area AA for displaying input images. The pixel array is arranged in the active area AA. The pixel array includes a plurality of data lines 102, a plurality of gate lines 104 crossing the data lines 102, a plurality of sensing lines 103, and pixels arranged in a matrix.

Each pixel can be divided into red sub-pixels, green sub-pixels, and blue sub-pixels for color representation. Each pixel may further include white sub-pixels. Each sub-pixel 101 includes a pixel circuit.

The touch sensor may be disposed on the display panel 100. The touch input can be sensed using touch sensors or through pixels. The touch sensor can be implemented as an on-cell type or add-on type touch sensor arranged on the screen of the display panel, or as an embedded in a pixel array In-cell type touch sensor.

The display panel driving circuits 110, 112, and 120 include a data driver 110 and a gate driver 120. The demultiplexer 112 may be disposed between the data driver 110 and the data line 102. The demultiplexer 112 can be omitted.

In the normal driving mode, under the control of the timing controller (TCON) 130, the display panel driving circuits 110, 112, and 120 write the input image data into the pixels on the display panel 100 to display the input on the screen image. The display panel driving circuits 110, 112, and 120 may further include a touch sensor driver for driving the touch sensor. The touch sensor driver is omitted in FIG. 1. In a mobile device or a wearable device, the data driver 110, the timing controller 130, and the power supply part 140 may be combined in a single integrated circuit.

When the input voltage Vin is supplied from the host system 200, the power supply part 140 generates power required to drive the timing controller 130, the display panel driving circuits 110, 112, 120, and the display panel 100. The power supply part 140 outputs the gamma reference voltage GMA, the gate high voltage VGH, the gate low voltage VGL, and so on. The gamma reference voltage GMA can be divided into a voltage for each gray scale, converted into a gamma compensation voltage, and provided to a digital-to-analog converter (hereinafter referred to as "DAC") for the data driver 110. The power supply part 140 may be implemented as a power supply IC including a charge pump, a regulator, a buck converter, a boost converter, and the like.

The data driver 110 converts the digital data of the input image received from the timing controller 130 into a gamma-compensated voltage to generate a data voltage Vdata. The data voltage Vdata is applied to the pixel through the demultiplexer 112 and the data line 102.

The demultiplexer 112 is disposed between the data driver 110 and the data line 102 to distribute the data voltage Vdata output from the data driver 110 to the data line 102 by using a plurality of switching elements. A single channel of the data driver 110 is time-divided, and is connected to the data line 102 through the demultiplexer 112, thereby reducing the number of the data line 102.

The gate driver 120 may be implemented as a gate in panel (GIP) circuit in the panel, which is directly formed in the bezel area on the display panel 100 together with the TFT array in the active area AA. The gate driver 120 outputs the gate signal to the gate line 104 under the control of the timing controller 130. The gate driver 120 can sequentially provide gate signals to the gate line 104 by shifting these signals through the shift register. The gate signal may include, but is not limited to, the scan signal SCAN and the sensing signal SENSE.

The timing controller 130 receives the digital image data DATA of the input image and the timing signal synchronized therewith from the host system 200. The timing signal includes a vertical synchronization signal (Vsync), a horizontal synchronization signal (Hsync), a clock signal, and a data enable signal (DE).

The timing controller 130 can adjust the frame rate to be higher than the input frame frequency. For example, the timing controller 130 may control the operating timing of the display panel driving circuits 110, 112, and 120 by multiplying the input frame frequency (Hz) by i times (i is a positive integer greater than 0). The frame frequency is 60 Hz in the National Television Standards Committee (NTSC) system, and 50 Hz in the Phase-Alternating Line (PAL) system. The timing controller 130 may reduce the frame frequency to between 1 Hz and 30 Hz, so as to reduce the refresh rate of the pixels in the low-power driving mode.

The timing controller 130 generates data timing control signals for controlling the operation timing of the display panel driving circuits 110, 112, and 120 and the external compensation circuits 103, 111, and 131 based on the timing signals Vsync, Hsync, and DE received from the host system 200 . The gate timing control signal output from the timing controller 130 can be converted into a gate high voltage VGH or a gate low voltage VGL by a level shifter (not shown), and provided to the gate driver 120. The level shifter converts the low level voltage of the gate timing control signal into a gate low voltage VGL, and converts the high level voltage of the gate timing control signal into a gate high voltage VGH.

The timing controller 130 or the host system 200 is used as a control part, which stores and updates defective pixel information and controls defect reports. If the number of progressively defective pixels is greater than a predetermined reference value for defect management and control, the timing controller 130 or the host system 200 sends a defect report to the service center 300.

The compensator 131 of the timing controller 130 stores the information about the defective pixels sensed in real time in the non-volatile memory 132b. The defective pixel information is divided into defective pixel information and defective candidate information.

The defective pixel information includes: the number of defective pixels detected before the product is shipped; the number of defective pixels sensed after the product is shipped; the location of the defective pixel; and information on whether the display panel is defective. Defective pixels are classified into pixel defects and sub-pixel defects. The defective pixel can be regarded as a dark spot on the screen of the display panel. The defective pixel information may include defective pixel information of each pixel and defective pixel information of each sub-pixel.

If the number of defective pixels is greater than the preset reference value for defect management and control, a defect mark indicating a defect may appear. If the defect flag is 1 (high), it means that the number of defective pixels in the display panel is greater than the preset reference value for defect management. The display panel 100 with the defect mark is discarded before the product is shipped, and is automatically reported to the service center 300 via the wired/wireless network 210 as a defective panel. When a defect mark occurs, the timing controller 130 accesses the defective pixel information stored in the non-volatile memory 132b, and automatically sends the defective pixel information to the host system 200.

The compensator 131 of the external compensation circuits 103, 111, and 131 can detect defective pixels based on the real-time sensing results on the driving element. In addition, the compensator 131 can set a compensation value and update the compensation value based on the real-time sensing result on the electrical characteristics of the driving element, and select defect candidates within the compensation range, wherein the electrical characteristics of the driving element DT are compensated by the compensation value.

The defect candidate information includes information about the defect candidate pixel. When the stress on the driving element accumulates after the product is shipped, the defective pixel is likely to evolve into a dark spot defect or a bright spot defect. The defect candidate information may include the number of defect candidate pixels, the location of the defect candidate pixels, and information about whether the display panel is defective. Defect candidate pixels are classified into defective pixels and defective sub-pixels. The defect candidate information may include information of each pixel and information of each sub-pixel.

If the number of defect candidate pixels is greater than the preset reference value for defect management and control, a defect prediction mark may appear. If the defect prediction flag is 1 (high), it means that the number of defect candidate pixels in the display panel 100 is greater than the preset reference value for defect management. As shown in FIG. 10, if a defect prediction mark appears when the user uses the display device, the display device can automatically send a defect report to the service center 300 via the wired/wireless network 210. When the defect prediction flag appears, the timing controller 130 can access the defect candidate information stored in the non-volatile memory 132b, and automatically send the defect candidate information to the host system 200. The compensation member 131 of the external compensation circuits 103, 111, and 131 may update the defect prediction flag together with the defect candidate information based on the defect candidate sensing result obtained in the sensing mode.

The timing controller 130 can access the defective pixel information stored in the non-volatile memory 132b and send it to the host system 200 in response to a request from the host system 200, regardless of whether there is a defect flag.

The host system 200 may be one of the following: a television system, a digital set-top box, a navigation system, a personal computer, a home theater system, a mobile device, and a wearable device. The host system 200 is connected to the service center 300 via a wired/wireless network 210. Upon request from the user or the service center 300, the host system 200 may receive defective pixel information from the timing controller 130 and display it to the user or send a defect report to the service center 300. The defect report may include either or both of defective pixel information and defect candidate information.

Users can request defective pixel information through user interfaces such as remote controls, touch screens, and keyboards. When receiving a user command regarding defective pixel information via the user interface, the host system 200 may transmit the user command to the timing controller 130 and display the defective pixel information on the screen of the display panel 100, or may control the timing The defective pixel information received by the detector 130 is sent to the smartphone of a given user.

The service center 300 can request defective pixel information from the host system 200 via a wired/wireless network. When receiving the request information about defective pixel information from the service center 300, the host system 200 requests the defective pixel information from the timing controller 130, and sends the defective pixel information received from the timing controller 130 to the service center 300.

When a defect mark or a defect prediction mark appears, the host system 200 may automatically send the defect information received from the timing controller 130 to the service center 300.

As shown in FIG. 2, the external compensation circuits 103, 111, and 131 include a sensing line 103 connected to the pixel circuit, a sensing element 111, and a compensation element 131 that receives sensing data (digital data) from the sensing element 111. The DAC of the data driver 110 and the sensing element 111 may be combined in the power driving IC (integrated circuit) 110a of the data driver 110 (as shown in FIG. 3). The compensator 131 may be embedded in the timing controller 130.

The external compensation circuits 103, 111, and 131 can sense the electrical characteristics of the driving element DT by initializing the source voltage of the driving element DT and the sensing line 103, that is, the voltage of the second node n2, as the reference voltage Vref, and then sensing Measure the source voltage of the driving element DT. The electrical characteristics of the driving element DT that can be sensed include a threshold voltage Vth and a mobility μ. In the sensing mode, the sensing element 111 can sample the voltage on the sensing line 103 and convert it into digital data through an analog-to-digital converter (hereinafter referred to as “ADC”) to generate sensing data.

The sensing element 111 may include ADC, switching elements M3 and M4, and the like. The switching element M3 may provide a predetermined reference voltage Vref to the sensing line 103 to initialize the source voltage of the driving element DT to the reference voltage Vref. The switching element M4 may be turned on after the switching element M3 is turned off to provide the source voltage of the driving element DT to the ADC. The ADC can convert the analog sensing voltage on the sensing line 103 into digital data and send it to the compensator 131.

The compensator 131 can sense the mobility μ of the driving element in each sub-pixel based on a change in the source voltage of the driving element during a preset movement sensing period. The compensator 131 recognizes the gate voltage of the driving element in each sub-pixel, that is, the data voltage Vdata, as the pixel data stored in the memory of the timing controller 130, because the data voltage is applied to the gate of the driving element. The compensator 131 senses the threshold voltage Vth of the driving element by finding that the gate-source voltage of the driving element DT in each sub-pixel is equal to Vth based on the difference between the pixel data and the sensing data.

The compensator 131 senses changes in the electrical characteristics of the driving element DT in each sub-pixel, and sets a compensation value based on the sensing result. The compensation value is proportional to the change in the electrical characteristics μ and Vth of the driving element DT. The compensation value is updated based on the real-time sensing result. The compensator 131 modulates the pixel data by the compensation value obtained from the sensing result and sends it to the data driver 110 through the timing controller 130 to compensate the electrical characteristics of the driving element DT. The data driver 110 converts the pixel data modulated by the compensation component 131 into a data voltage Vdata, and outputs it to the data line 102. The compensation member 131 may be provided in the timing controller 130.

As in the example of FIG. 2, the pixel circuit includes an OLED, a driving element DT connected to the OLED, a plurality of switching elements M1 and M2, and a capacitor Cst. It should be noted that the pixel circuit is not limited to the pixel circuit shown in FIG. 2. The driving element DT and the switching elements M1 and M2 are implemented as n-channel transistors NMOS in FIG. 2, but are not limited thereto.

The OLED is a light-emitting diode, which emits light through a current generated according to the gate-source voltage of the driving element DT, and the current varies with the data voltage Vdata. The OLED includes an organic compound layer formed between the anode and the cathode. The organic compound layer may include, but is not limited to, a hole injection layer HIL, a hole transport layer HTL, a light emitting layer EML, an electron transport layer ETL, and an electron injection layer EIL. The anode of the OLED is connected to the driving element DT via the second node n2, and the cathode of the OLED is connected to the VSS electrode, to which the low-level power supply voltage VSS is supplied. In Figure 2, "Coled" represents the parasitic capacitance of the OLED.

The first switching element M1 is turned on in response to the scan signal SCAN, and provides the data voltage Vdata to the gate of the driving element DT connected to the first node n1. The first switching element M1 includes a gate connected to the first gate line 1041 to which the scan signal SCAN is applied, a first electrode connected to the data line 102, and a second electrode connected to the first node n1.

The second switching element M2 is turned on in response to the sensing signal SENSE to provide the reference voltage Vref to the second node n2. The second switching element M2 includes a gate connected to the second gate line 1042 to which the sensing signal SENSE is applied, a first electrode connected to the sensing line 103 to which the reference voltage Vref is applied, and a second electrode connected to the second node n2 .

The driving element DT supplies current to the OLED according to its gate-source voltage. The driving element DT includes a gate connected to the first node n1, a first electrode that supplies the pixel driving voltage VDD, and a second electrode connected to the anode of the OLED via the second node n2.

The capacitor Cst is connected between the first node n1 and the second node n2. The voltage of the capacitor Cst is the gate-source voltage of the driving element DT.

FIG. 3 is a view showing a circuit board connected to the display panel 100.

3, the circuit board includes a source printed circuit board (PCB) 114 connected to the power driving IC 110a and a control board 134 connected to the source PCB 114. The timing controller 130, the memory 132, and the power supply part 140 are installed on the control board 134. The timing controller 130 may include a compensator 131.

As shown in FIG. 4, the memory 132 may include a volatile memory 132a and a writable non-volatile memory (hereinafter referred to as "non-volatile memory") 132b. Under the control of the timing controller 130, the volatile memory 132a temporarily stores the real-time sensing result and compensation value, and the electroluminescent display is powered on at the same time. When the electroluminescent display is powered on, the volatile memory 132a receives the data stored in the non-volatile memory 132b from the timing controller 130, and before the electroluminescent display is powered off, the real-time sense is stored in the timing controller 130 Test results and updated compensation values. The timing controller 130 sends the data read from the volatile memory 132a to the non-volatile memory 132b, and stores the sub-pixel driving history, the cumulative value of the sensing result, and the updated compensation value in the non-volatile memory 132b. In the memory 132b.

The non-volatile memory 132b stores the register setting value of the timing control signal used for the timing controller 130, the history of sub-pixel driving, the change of the electrical characteristics of the driving element accumulated based on the sensing result, and the update based on the sensing result The compensation value and defective pixel information. The non-volatile memory 132b stores data that needs to be accumulated, because even if the electroluminescent display is powered off, the stored data will not be erased. The volatile memory 132a can be implemented as a double data rate (DDR) RAM, but is not limited to this, and the non-volatile memory 132b can be implemented as a NAND flash memory, but is not limited to this.

By updating the real-time sensing result, compensation value, and defective pixel information and storing them in the non-volatile memory 132b, the compensator 131 of the external compensation circuit can detect progressively defective pixels in real time. It is caused by the deviation of the threshold voltage of the driving element DT after delivery.

The control board 134 is connected to the main board of the host system 200. The service center 300 can directly access the non-volatile memory 132b through the connector of the control board 134 to read the defective pixel information.

The electroluminescent display of the present invention detects defective pixels in real time based on the sensing results on the driving elements obtained by the external compensation circuits 103, 111, and 131 after the product is shipped. Defective pixels include defective pixels in sub-pixels and defective pixels in pixels. After the product is shipped, the sensing mode can be divided as shown in FIG. 5.

Fig. 5 is a view showing the inspection mode after the product is shipped. Fig. 6 is a view showing in detail the effective interval AT and the vertical blanking interval VS.

Referring to Figure 5 and Figure 6, the sensing mode is divided into before and after product shipment. The threshold voltage Vth and the mobility μ of the driving element DT in each sub-pixel are sensed through the sensing path connected to the pixel before the product is shipped, and then, the electrical of the driving element DT in each sub-pixel is compensated based on the sensing result Changes in characteristics Vth and μ. In the sensing mode before the product is shipped, the mobility μ of the driving element DT in each sub-pixel and the compensation value of the threshold voltage Vth are stored in the memory 132.

The sensing mode after the product is shipped includes: a first sensing mode executed in the power-on sequence; a second sensing mode for instantaneously sensing the electrical characteristics of the driving element DT during display driving in the normal driving mode; The third sensing mode executed in the electrical sequence.

When the electroluminescent display is powered on and the input voltage Vin is generated from the host system 200, the power-on sequence ON starts. In the power-on sequence ON, the driving voltages for the display panel driving circuits 110, 112, and 120 and the display panel 100 are generated, and the timing controller 130 and the display panel driving circuits 110, 112, and 120 are reset. After the power-on sequence is ON, the external compensation circuits 103, 111, and 131 immediately operate in the first sensing mode. The external compensation circuits 103, 111, and 131 instantly sense the mobility μ of the driving element DT in each sub-pixel, and update the compensation value based on the sensing result.

When the first sensing mode is completed, the display panel driving circuits 110, 112, and 120 operate in the normal driving mode to write the pixel data of the input image to the pixels on the display panel 100 during the effective interval AT of each frame. And the input image is displayed on the screen of the display panel 100. In addition, the external compensation circuits 103, 111, and 131 perform the second sensing mode during the display driving period of the normal driving mode to instantly sense the driving element in each sub-pixel during the vertical blanking interval VB of each frame. The mobility μ of DT, and the compensation value is updated based on the sensing result.

After receiving the power-off signal for the electroluminescent display, the power-off sequence OFF starts. In the third sensing mode, the external compensation circuits 103, 111, and 131 sense the threshold voltage Vth of the driving element DT in each sub-pixel during a preset delay timing period before the power-off sequence is OFF.

The effective interval AT is a time sequence during which the data of a frame is written to all pixels on the screen. The vertical blanking interval VB is a blanking period during which no pixel data of the input image is received between the effective interval AT of the (N-1)th frame and the effective interval AT of the Nth frame. During the vertical blanking interval VB, the timing controller 130 does not receive the data of the next frame (the Nth frame data).

The vertical synchronization signal Vsync defines a frame. The horizontal synchronization signal Hsync defines a horizontal time sequence (horizontal time). The data enable signal DE defines the duration of valid data including pixel data to be displayed on the screen.

The data enable signal DE is synchronized with the effective data to be displayed in the pixel array of the display panel 100. The 1 pulse interval of the data enable signal DE is 1 horizontal time sequence, and the high logic part of the data enable signal DE represents the time sequence of inputting pixel data of 1 pixel line. The 1-horizontal timing 1H is the time required to write data into one pixel line of the pixels on the display panel 100.

The timing controller 130 receives the data enable signal DE and the input image data during the effective interval AT. During the vertical blanking interval VB, the data enabling signal DE and the input image data are not provided. During the effective interval AT, the timing controller 130 receives data of 1 frame to be written to all pixels. 1 The frame is the sum of the effective interval AT and the vertical blanking interval VB.

It can be seen from the data enable signal DE that the display device will not receive input data during the vertical blanking interval VB. The vertical blanking interval VB includes a vertical blanking timing VS, a vertical sync pulse end timing FP (Vertical front porch), and a vertical sync pulse start timing BP (Vertical back porch).

In the present invention, defective pixels are detected based on the threshold voltage sensing result on the driving element, and the accumulated compensation value obtained from the threshold voltage sensing result on the driving element is updated in the non-volatile memory 132b, so that the product Detect progressively defective pixels after shipment.

FIG. 7 is a flowchart showing a method for controlling defective pixels before the product is shipped in an electroluminescent display according to an exemplary aspect of the present invention. FIG. 8 is a flowchart showing a method for controlling defective pixels after the product is shipped in an electroluminescent display according to an exemplary aspect of the present invention. FIG. 9 is a flowchart showing in detail a method for controlling defective pixels if the variation of the threshold voltage of the driving element is within the normal and compensable range in FIG. 8.

7-9, the external compensation circuits 103, 111, and 131 detect defective pixels based on the sensing results on the threshold voltage Vth of the driving element in the sensing mode before product shipment, and store the defective pixel information in non-volatile Sexual memory 132b (S01 to S02). If the number of detected defective pixels is greater than the predetermined reference value TH for defect management and control, the corresponding product is discarded (S03 to S04). If the number of detected defective pixels is less than the predetermined reference value TH for defect management and control, the corresponding product is shipped with the defective pixel information stored in the non-volatile memory 132b.

The manufacturer of the display module can provide the display module to the assembler. The display module includes a display panel and its driving circuit. The assembler connects the host system with the display module provided by the manufacturer. The display module manufacturer can store the defective pixel information generated before shipment in the non-volatile memory 132b and provide it to the assembler.

Referring to FIG. 8, when the stress on the driving element DT is accumulated, the threshold voltage Vth of the driving element DT is shifted according to the history of pixel driving after the product is shipped (S11).

The external compensation circuits 103, 111, and 131 sense the threshold voltage Vth of the driving element DT in each sub-pixel, and determine whether the threshold voltage Vth of the driving element DT in each sub-pixel is within the normal range (S12 and S13 ). The compensation value of each sub-pixel is determined in proportion to the sensed variation of the threshold voltage of the driving element DT of each sub-pixel. The compensation value of each pixel is updated based on the real-time sensing result. The normal range refers to the variation of the threshold voltage of the driving element DT, whereby it can compensate for the deviation of the threshold voltage of the driving element DT. The abnormal range beyond the normal range means that the driving element DT has progressed to the extent that the deviation of the threshold voltage of the driving element DT cannot be compensated. In the abnormal range, the deviation of the threshold voltage of the driving element DT cannot be compensated by the compensation value in the normal range.

In step S13, if it is sensed that the variation ΔVth of the threshold voltage of the driving element DT in each sub-pixel is in the abnormal range, the corresponding sub-pixel is counted as a defective pixel, and the defective pixel information is updated (S14). If the accumulated number of defective pixels is greater than the predetermined reference value TH for defect management and control, a defect flag "1" appears, the defect pixel information reflecting the defect flag is updated, and the defect report is sent to the service center 300 (S15, S16, and S17) ). Defective pixel information can be attached to the defect report.

Referring to FIG. 9, in step S13, the variation ΔVth of the threshold voltage of the driving element DT in each sub-pixel can be sensed in the normal and compensable range. In this case, the compensation value determined based on the sensing result on the threshold voltage Vth is compared with the first threshold value LIM1 and the second threshold value LIM2. The first critical value LIM1 can be set to a specific value smaller than the upper limit compensation value in the normal range, and the second critical value LIM2 can be set to a specific value larger than the lower limit compensation value in the normal range. The first critical value LIM1 is a value greater than the second critical value LIM2. The critical values LIM1 and LIM2 can be appropriately selected according to the defect management strategy and the characteristics of the display panel.

As the light-emitting time of the pixel passes, the driving element DT receives a positive stress, and its threshold voltage Vth shifts to a positive voltage. The positive shift of the threshold voltage Vth of the driving element DT increases the compensation value, and the compensator 131 compares the updated compensation value with the first threshold value LIM1 based on the sensing result (S21 and S22). If the compensation value is greater than the first critical value LIM1, the corresponding sub-pixel is likely to evolve into a defective pixel defect.

In the case of a non-luminous pixel (or sub-pixel), the driving element DT is subjected to negative stress and its threshold voltage Vth shifts to a negative voltage. The negative shift of the threshold voltage Vth of the driving element DT reduces the compensation value. If the compensation value is less than the second critical value LIM2, the corresponding sub-pixel is likely to evolve into a defective pixel defect. The compensator 131 compares the updated compensation value with the second critical value LIM2 based on the sensing result (S21 and S29).

In the present invention, the compensation value based on the instant sensing result is compared with the first critical value LIM and the second critical value LIM2, and it is likely to evolve into a dark spot defect or a bright spot defect due to the positive shift of the threshold voltage Vth. Pixels (or sub-pixels) are counted as "defective pixels" and counted up. If the compensation value is greater than the first critical value LIM1 (S22), the count of defect candidates is accumulated (S23); if the compensation value is less than the second critical value LIM2 (S29), the count of defect candidates is also accumulated (S30).

If the cumulative count of defect candidates is greater than the reference value TH1 for defect management and control, the defect prediction flag PIX _f becomes 1, and the defect candidate information is updated based on this defect prediction flag PIX _f (S24, S25, S27, S31, S32 , And S34). When the defect prediction flag PIX _f =1 appears, the defect report can be automatically sent to the service center 300 (S28 and S35). The defect candidate pixel information can be attached to the defect report. In steps S24 and S31, if the cumulative count of defect candidates is smaller than the reference value TH1 for defect management, the defect prediction flag PIX _f remains at 0 (zero) (S26 and S33).

When the defect prediction flag PIX _f appears, the defect report information can be displayed on the screen of the display panel 100 to notify the user of this. If the cumulative count of defect candidates is less than the reference value TH1 for defect management and control, the defect prediction flag PIX _f remains at 0.

As described above, in the present invention, it is possible to instantaneously detect defective pixels and defect candidate pixels that are likely to evolve into dark spots or bright spots or defective pixels based on the instant sensing results on changes in the electrical characteristics of the driving element. Therefore, the present invention allows the defect candidate pixels and defective pixels in the electroluminescent display to be detected immediately after the product is shipped, and also allows the defective pixel information stored in the memory to be updated based on the real-time sensing result on the driving element.

In the present invention, if the number of defective pixels or defect candidate pixels detected based on the instant sensing result on the driving element exceeds the reference value for defect management and control, the defect report can be automatically sent to the service center, or The defect report information is displayed on the screen to notify the user of the current defect level of the product.

Although the various aspects have been described with reference to their various illustrative aspects, it should be understood that those with ordinary knowledge in the field can design many other modifications and aspects, and these modifications and aspects will fall within the scope of the principles of the present invention . More specifically, various changes and modifications can be made in the arrangement of component parts and/or subordinate assembly arrangements within the scope of the present invention, the drawings, and the appended claims. In addition to changes and modifications of component parts and/or arrangements, the use of alternative solutions is also obvious to those with ordinary knowledge in the field.

This application claims the priority rights of Korean Patent Application No. 10-2017-0175985 filed on December 20, 2017, and for all purposes, the entire contents of which are incorporated herein by reference as if fully stated herein.

100‧‧‧Display Panel

101‧‧‧sub pixel

102‧‧‧Data line

104‧‧‧Gate line

110‧‧‧Data Driver (Display Panel Drive Circuit)

112‧‧‧Demultiplexer (display panel drive circuit)

120‧‧‧Gate Driver (Display Panel Drive Circuit)

130‧‧‧Timing Controller

131‧‧‧Compensation part (external compensation circuit)

132‧‧‧Memory

140‧‧‧Power section

200‧‧‧Host System

210‧‧‧Wired/Wireless Network

300‧‧‧Service Center

AA‧‧‧Active area

GMA‧‧‧Gamma reference voltage

VGH‧‧‧High gate voltage

VGL‧‧‧Low gate voltage

Vin‧‧‧Input voltage

Claims (17)

An electroluminescent display, including: a display panel, including a plurality of data lines, a plurality of gate lines crossing the plurality of data lines, and a plurality of pixels with a plurality of sub-pixels, and each pixel includes A driving element that drives a light-emitting diode; a compensation element, based on the sensing result of the electrical characteristics of the driving element in each of the plurality of sub-pixels, detecting defective pixels from the pixels, the sensing The measurement result is obtained by a sensing element connected to the driving element in real time; and a memory for storing defective pixel information about the defective pixels, wherein the compensation element is based on sensing on a threshold voltage of the driving element As a result, a compensation value is updated, and if the number of defective pixels is greater than a reference value for defect management, a defect mark appears, and wherein the compensation element is based on each of the sub-pixels obtained by the sensing element One of the sensing results on the electrical characteristics of the driving element, if the threshold voltage variation of the driving element is within a normal and compensable range, then the electrical characteristics of the driving element in each sub-pixel The characteristic sensing result is compared with a preset threshold value to determine a potentially defective pixel. According to the electroluminescent display described in item 1 of the scope of patent application, the defective pixel information includes the position of the defective pixels and information about whether the display panel is defective. The electroluminescent display described in item 1 of the scope of patent application, wherein when the defect mark appears, a defect report is sent to an external service center via a wired/wireless network. The electroluminescent display according to the first item of the scope of patent application, wherein when the defect mark appears, a predetermined defect report information is displayed on a screen of the display panel. The electroluminescent display described in item 3 of the scope of patent application, wherein the defect report includes the defective pixel information. According to the electroluminescent display described in item 1 of the scope of patent application, the compensation element compares a compensation value based on the sensing result of the electrical characteristics of the driving element with a first threshold value, and if the compensation is If the value is greater than the first critical value, the count of the potentially defective pixels is accumulated. The electroluminescent display according to item 6 of the scope of patent application, wherein the compensation component compares the compensation value with a second threshold value less than the first threshold value, and accumulates the count of the potentially defective pixels, and If the compensation value is less than the second critical value, then the count of the potentially defective pixel is accumulated and the information about the potential defective pixel is updated, and if the accumulated count of the potentially defective pixel is greater than a reference value for defect management, issue A defect prediction mark. The electroluminescent display described in item 7 of the scope of patent application, wherein, when the defect prediction mark appears, a defect report is sent to an external service center via a wired/wireless network. According to the electroluminescent display described in item 7 of the scope of patent application, when the defect prediction mark appears, a predetermined defect report information is displayed on a screen of the display panel. The electroluminescent display described in item 8 of the scope of patent application, wherein the defect report includes information on potentially defective pixels. An electroluminescent display includes: a display panel including a plurality of pixels, each pixel includes a plurality of sub-pixels, and each pixel includes a driving element for driving a light-emitting diode; a sensing element, Connected to the driving element, and real-time sensing of the electrical characteristics of the driving element in each of the plurality of sub-pixels; a compensating part, detecting defective pixels in the plurality of pixels based on the sensing result, and updating based on the sensing result A compensation value, and if the number of the defective pixels is greater than a reference value for defect management, a defect mark is generated on the display panel; and a memory storing a defective pixel information about the defective pixels, The defective pixel information includes the positions of the defective pixels, wherein the compensation element is based on the sensing result of the electrical characteristics of the driving element in each of the sub-pixels obtained by the sensing element, if the driving element The change of a threshold voltage is within a normal and compensable range, and a potential defect is determined by comparing the sensing result of the electrical characteristics of the driving element in each sub-pixel with a preset threshold value Pixels. The electroluminescent display described in item 11 of the scope of patent application, wherein, when the defect mark is generated, the compensation piece sends a defect report to an external service center via a wired/wireless network. The electroluminescent display according to item 11 of the scope of patent application, wherein the compensation element compares a compensation value based on the sensing result of the electrical characteristics of the driving element with a first threshold value, and if the compensation is If the value is greater than the first critical value, the count of the potentially defective pixels is accumulated. The electroluminescent display according to item 13 of the scope of patent application, wherein the compensation component compares the compensation value with a second threshold value smaller than the first threshold value, and accumulates the count of the potentially defective pixels, and If the compensation value is less than the second critical value, then the count of the potentially defective pixel is accumulated and the information about the potentially defective pixel is updated, and if the accumulated count of the potentially defective pixel is greater than a reference value for defect management and control, then Issue a defect prediction flag. The electroluminescent display according to item 14 of the scope of patent application, wherein when the defect prediction mark appears, the display panel displays a predetermined defect report information. An electroluminescent display, including: a display panel, including a plurality of data lines, a plurality of gate lines crossing the data lines, and a plurality of pixels, each pixel includes a light emitting diode A driving element; a compensating element, which sets a compensation value based on a sensing result of the electrical characteristics of the driving element in each sub-pixel of the pixels, the sensing result is determined by a sensing element connected to the driving element Obtain and select a potentially defective pixel among the pixels in a compensation range, wherein the electrical characteristics of the driving element are compensated by the compensation value; and a memory storing a potentially defective pixel information, the potentially defective pixel information includes The number of the potentially defective pixels, where the compensation element is based on the sensing result of the electrical characteristics of the driving element in each of the sub-pixels obtained by the sensing element, if a threshold voltage of the driving element The change amount of is within a normal and compensable range, and a potentially defective pixel is determined by comparing the sensing result of the electrical characteristics of the driving element in each sub-pixel with a preset threshold value. A method for controlling defective pixels on an electroluminescence display, the electroluminescence display comprising a display panel, the display panel including a plurality of data lines, a plurality of gate lines crossing the data lines, and a plurality of pixels, Each pixel includes a driving element for driving a light emitting diode, and the method includes: detecting defective pixels from the pixels based on the sensing result of the electrical characteristics of the driving element; Set a compensation value based on the sensing result on the electrical characteristics of the driving element, and select defect candidates from the pixels within a compensation range, wherein the electrical characteristics of the driving element are compensated by the compensation value; and The defective pixel information of the defective pixels and potentially defective pixels is stored in a memory, wherein, based on the sensing result of the electrical characteristics of the driving element, if the variation of a threshold voltage of the driving element is a normal, Within the compensable range, a potentially defective pixel is determined by comparing the sensing result of the electrical characteristics of the driving element in each sub-pixel of the pixel with a preset threshold value.

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